Scientists have found numerous ways to measure pollution in the environment, and some of these unconventional methods rely on indicator species. By measuring the population change of an individual indicator species, scientists can draw conclusions about changes in levels of a certain pollutant. In addition, this method of measuring pollution demonstrates the impact of pollution on vulnerable species.

Lichens and Air Pollution

One of the most common indicator species used to measure air pollution are lichens. Lichens are similar to fungi and algae, and absorb water and minerals from the air to grow on living and nonliving surfaces. As such, lichens absorb all the pollutants in the environment, and some varieties of lichen survive better in the presence of pollution than others. Scientists have found that green and bushy lichen survive only in clean air, so the presence of many green and bushy lichens in a given environment indicates that the air is clean. Hard and crusty lichens, however, can survive quite well in the presence of pollution, and so an abundance of these species of lichen may indicate that the air in the environment is polluted.

Aquatic Invertebrates and Water Pollution

Different species of aquatic invertebrates can survive in polluted water, while others cannot. As such, scientists often take a sample of the invertebrates living in a water source and use the species in the sample to assess the level of pollution in the water. A sample with invertebrates like fresh water shrimp and mayfly larva indicates clean water, because these species have very low tolerance for any pollution. If scientists find water with many rat-tailed maggots or sludge worms, however, they can be sure that the water is highly polluted because these species survive well in polluted waters.

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Fish Survival and Water Oxygen

One simple way to measure the health of a given water source is to examine the survival of fish in that source of water. Fish rely heavily on the dissolved oxygen in water to survive, so if oxygen levels are low due to pollution, no varieties of fish will survive. Scientists can get especially important insights from fish populations by monitoring their change over time. If a lake or pond once had a large fish population, but that population is in rapid decline, scientists can infer that pollution levels are growing in the lake or pond.

Biodiversity as a General Measure

More broadly, scientists can use all the species living in a given area as a collective indicator species. This is because living things that can survive in the presence of pollution are quite rare. As such, places that are highly polluted will not support a diverse range of species. The less ecologically diverse a region is, the more polluted it is. This is true for both land and water ecosystems. Regions with very little life are likely to be highly polluted, while places teeming with life are likely to be very clean.

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About the Author

Kevin Wandrei has written extensively on higher education. His work has been published with Kaplan, Textbooks.com, and Shmoop, Inc., among others. He is currently pursuing a Master of Public Administration at Cornell University.